Draft regulator



Sept. 16, 1941. I G. DALEN ETAL 2 37 DRAFT REGULATOR Filed June 17, 19574' sreets-setz BY ATTORNEY Sept- 6, 1941.

ETAL DRAFT REGULATOR Filed June 17, 1937 4 shans-Sheet 3 open.

nama,... s, 1941" UNITED' -STATE -PAT nammamrot corporation o! j Swedeni Application :mm 1937, s m Sweden .me zz. oss

Dal en ,andfGe'org Karl Johanson, Lidingo, sweden; asignors %SvenskaAktie boiagetGasaccumulator. Sto'c kl'olm; Sweden. a v

fa Ciaim's (ci. zaa-easy The present invention reiers -.to combustiondevices, and particularly to co'ntinuously burn devices withintermittent heat output anchas cooking 'toves ,and the like, andprovided with thermostatic means !or regulating .the draft.

The combustion has hitherto usually been regulated by means oi athermostatically operated valve in the air inlet ,to the fire box.However, such a `devic e has the disadvantagethat it, be-

comes inoperative when the ashpit door isleit open which often happens'when the stove 'is attended by unskiled persona on such occasions a ,toorapid 'combustion is obtained and the internalwparts of the by excessiveheat.

It, has heretofore been stove may be destroyed E" to arrange the draft'regulating device-intthe flue, which conducts the combustion 'gases rromthe fire box. 'Ihisdevicewill then reduce the draft through the 'firebox when the temperature oi the 'combustion gasesincreases and preventstoo rapid combustion, even it Devices' oi condensation and soot collectin the hue; thus the' ashpit door is' ieit tully this kind hithertoknown, hawe do not operate satisiacto'riiy. Drincipally because Thislocationiis to be preierredi part ybec i the temperature oi the iluethere 'is relatively o a d pa t y because, the regulating member isprotected against particles of ash or iuel aboutintheflrebo i\ h\ hePlacing oi!` the movable draft regulating member 'in the iiue also hasthe advantage that the member can beplaced near to the'heat 'sensii tivemember of the ;regulating device or evenbe built. together therewith to!oi-m( one. unit, In this way the connection between the two memv berswillbe as simple as possible'. However, there i are alsofreasons !orpiacing the members separatelyl In cooking stoves of the .kind thatfhas'one hot platein intimate heat transmitting contactwith the flre, atleast `one other-:hotplate which receives heat from the iiue gasesand atleast; o'ne oven, the heat sensitive member. may

preferably .be in .relatively good v heat transmitz ting connection withthese parts of the stove a and also with the flue gases. `The heatresistance' hindering operation of V the movable member of i the draftregulating device. 'According -to the present invention thi's troubleis'obviated by the flue in'which the movable member oi'the'dr'aitregulating device is' located being heat insulated. :By` this meanstheflue' attains such 'a high temperature', even't' very' siight heatoutput ironi the stove, that condensation' and scot are prevented fromdepositingthereim If the invention 'is applied 'to' 'a continuouslyburning stove or the like with intermittent hefat output the flue mustbe' insulated at least-during the periods o! non-outpu" Duringtheseperiods the temperature oi the iiue will risehigh enough tobumawaythe soot and other'deposits..

jn; is not necessary' that me mie' be inslated' throughout its 4 entirelength; ',It -is 'most'i'm portant that the' part o! the flue between"the flre box and the movablemember of 'th ing device is weil 'Themovable draft' resuiating 'me mber may be located 'inany part oi theflue. -In combustion devices with one or severalplaces of heatwoutputat'which the combustion ga'ses give oil! their heat, such 'as cookingstoves, it may be placed' iii'` the part of the flue between the placeoi heat. output which is flrst'passed by the combustion' of thecombustion device.

gases and the chimn vice have a low heat cohductivity as in the'com vbetween the heat ksensitivemember and theabove mentioned part:: o! thestove is selected in such` aaway that thediflerent parts of the stoveare a I maintained at the desired temperat re. 'To aci complish this theheat sensitive member may placed relatively, near thehot plote thatreceivesc its heatdirectly i'rom 'the fire wlerep he-tem-` perature iscompar'atively high. The movable member. however, prei'erablymaybeplaced iar-. i

ther along inthe direction-..oi the flue gaslcurrent, where thetemperature-,is somewhat lower; This-is possible owing to the fact that'the flue' is` heat insulated so that no 'deposits o!.;'soot and tar.will .take place 'during periods oi' reduced heat output when is small;

:On the :oth should not'berin too. good heat conducting rela--` tionwith the heat accumulatingparts oi; the

combustiondevice, especially when theseparts haven great heat'accunulatingrcapa'cityh It is.

however, oi?` the greatest` importance that 'the heat sensitive memberis in relatively goodheat transmitting contact with thecombustiongases,especially when the parts of the combustion demon heat accumulatingcooking stoves' g" This'will be easily understoodj whengthe modeoi'operation oi' a heat accumulatingstove ot the common type isconsidered. Assume that` the "thermostat has been adius'ted for averageheat `emissi n and that the hot plate that lsin com munication with theheataccurx ulatoi' andalso h ENT OFFICE,

the heating eflect of. -flue gas i er hand the heat sensitivehember ahot plate thus remains comparativelyjcoo'l the regulatingj valvej willthen be automatically: set" 'to admt a largeairsupp y. This'results a'-rapid combustionin the fire box but, owing'to the existing between thefire and the hotplate, thei:

' stat to allow higherheat emission, thus further 'ncreasing the supply.of air to the flre box. Per?, i haps the ashpit door will' also beobenei A'very f high temperature will then arise in the firebo'x before'the heat accumulator is heatdahigh 1 v enoigh for the thermostatic:device to' limit "the i j tivly good f -hea`t`--' transmittance betweeni' the 1 emboqinients o! thirvention applied' to heat'ac'cumulating,cookingstoves the heat aceumulator its entirety arecooied down due to intense heat output. Itthe heat, i

:sensitive member is in` good heat conducting connection withthe ,hoataccumulating parts of the stovebut in relatively poor` beat transmitting5 connectionwith the combustion gases, the draft,

comparatively high heat conduction resistance temperature of the latterwill riseslowlyg Asthe kitchen stafl will `very likely'adjit the thermestov s'o' that thefjten'iperatureoffthese parte win influenceth'sensitive membervan d, on the member 'and i the 'combustion" gases in'oreler" OW V device-"an d that its draft regilating member-' re almostentirely when thefliie gases have reach'd a e certain; 'permissime'maximum temper ture: For ;the r'eg ulatinjg of' the temperature duringnorm'ai use of the combustion" device *another The 'draft through the'fire boxcan be 'regu` lated .in :different aways. 'I 'he resistance toflow; e of-flueiigas'es ins the-fine. can' be.varied,- for in-R` stancebyv restricting the passage bymeans of` K 4 v65 The gacompanyingdrawingsf show several,

1 on the lihet-S "of Fig; 7

missible 'limitet 60 i a. 1v a1ve,;:or` the= 'draft can. be:short-circu'ited by;

` dmissionof.atmospheric air throughag re'gu. lated openingin the fluepipe', OI course 't also ;possible fton -ombine these *two* a regulatingI methods2 w abesr 1- V Fi'g. 4, is a cross-sectiona view taken'onthe vu 'line l-l of Fli; 3; a

' Fig 5 is a cross-sectional view of 'a modification" of thedeviceshownin Figs. 3 and 4;

Fig. 6 is a cross-sectional view of -a further I embodinent ofaregulating device an dj is taken i Fi `g'.` 7 is a 'cross-sectionai'viewta ken on the of Fig. '6:

regulating device; a I across-section& view of an embodi- 'Fig. 8 is acrosssectional view of a 'further entjfof the' thermostatic regulatingdevice hav i wo" `h `eat; sehsitive members and istaken ef unaze-;se:off Fig 10;

Fg.- 10 is 'a'cross-sectionaiview'taken on ,the

;1ne`l9^ -l 0 oI-*Fi. 9; and i i 'Fi'g; 11 is a'cross-sectional view ofa -furthera regulating device with two heat sensitive memr bers.'; v ?i'-"Re fe` `{`*ing"moref' particuiafly to Big-1; refetence characterdesignates permanently open a air su'pply pipe to the ashpit andindicates the" fuel 'magazine projecting'finto the sri f coni stituteaheat accumulaton The top 'of 'the rue 'magazine forms a hot -plate 3,which may' 'bei a heatinsulated flue .i 5, e above" which another' 1 hotmate `S' is arranged-;which may be covered by aninsulatin g lid: Fromfiue 5 the fiuefgases V pass throig'h"an" opening' 'I into`thechimney`.1-

Below the hot plate `ath ottle val ve 8 is; ar: ranged which, whenclosed, 'as shown'iri Fig; 1`,.;

entirely closes the flu'e The valve :8 is 'actuated by a bimetal strip/&in such a way that it the valve tends to maintain a constant fluegastemperature; ;and vprevents' the temperature of i the :fire box, fromrisin'g orfalling beyondper- K strction; asjthe one ;shown in Fig icorresponding partsarefnarledlwith .the samet:: e e

too high flue 'gas temperatures; In this way,

temperatres, is "avoidei f nma I th i; i j tempe ature the parts ov zjtstove, ndsthe r 'firevvboxis regulated by mans ot a thermostat ic; iregulating device otwell knowmtypeu such a device is showndiagiainxnaticauy in?` Fig; z; `A

' withmerdury. The i'eceptacle loisplacein the fluj 5 heat t ansnittngconnection' with'the i 'a ium e' l n l i h th e gaes' ;being insertedina 'tube running croswise I through `the fine) When the tenz'erature ofthe receptacle rises, the merc'ury expanda'pressing on the walla o! theBourbon' tube' so that this tube becomes straighter. A "valve disc II,ar-` ranged at the free endoi' the Bourbon tube and disposed before theair inlet` opening l' to the ashpit, is thus moved-close: 'tothe openingand the air supply is reduced. When thetemperature ot the receptacle I ofalls, the air supply is increased by the Bourbon'tube 'becoming morecurved, so that the valve disc His withdrawn from theopening. Thisregulating device thua tends to maintain' a constant ,temperature in thefire box and the heat accumulator. i However, owing to the high heatcapacity of the' heat accumulator the: temperature will oscillateconsiderably. If, however, the temperature rises too much, theregulating device I', i' starts !unctioning, preventing the 'internalparts of stove from being damaged. i

Figs; 3'and 4 show on a larger scaleone embodiment of theregulating'device according to the inventionq A lid N is arranged in thehot' plate 6, located immediately above the flue 5. Under the lidthereis a partition ii in 'the' fiue, closing the flue with theexception ot'anjopening immediately below the lid' ll. In this open'- ing a flangel'S 'extends from the underside of the lid, in contact with the edge s'of the opening;

The flange is provided with an opening, in which a throttle valve l'l isarranged on a vertical shaft s, by means oi' which the opening canclosed. The valve !1 is supported on journalbearings' IS in the lid andin the -flange IS, and by means 'oi' I the a link is connected to oneend of a bimetallic strip 2l, the other end of which is fixed in a ro-21 of the hot plate S and suitably connected with a lever (not shown) onthe front side of the stove, by means of which it can be turned andadjusted. The adjusting screw 26 acts upon the lever 23' by `tatabeholder -22 supported by the'lid M. The i l holder is provided with 'alever 23, enabling it to means of an intermediate part 23, which isslidably mounted in the' lid and arranged opposite the regulating screw26 when 'the lid M "is *in its proper position. The intermediate part 28is pro vided with a colla- 29, preventing it' from being pushed out fromits bearing by the spring' 24 when the lid' |4 is removed and theintermediate part is no longer kept in position'by the adjusting screw26. In order to insure that the lid l4 is in' its proper position wheninserted in the hot p'late,

a projecting stud 30 is provided on the edge of the lid and isreceivable in acorresponding recess in the hot plate. also be arrangedin bearings'in the lid M so as to make it' removable together with thelid.

When the bimetal strip is cold it keeps the valve l'l open, but shutsthe same as the temper ature is increased. wh'en'the temperature hasreached a certain value the valve is' entirely' However. by setting*closed, as shown in Flg. 3. the holder 22 indiflerent positions, it ispossible to change the position of the' bimetal strip soas to make thevalve close 'at diiferent temp'eratures. As long as the temperature ofthe flue gases is below .a certainvalue, the valve is'kept open andHowever,'the adjusting screw may hot plate. This makes the-opening in thparti-` 'gases through 'the openings 32.

I 3 the" ilue ,gases !rom escping. The size or the tree opening and,consequentlmthe draltis reduced when thetemperature rises, and'increased u when the temperature'ralls'and the, valve, thus.

tends to maintain a constant, temperature of tiue gases." If desired,the bimetal strip maybe arranged in such a way that the valve isadjusted within wide temperature limits, or kept entirely open at lowertemperatures and 'closed rapidly. whei` he maximum permissibletemperature is reac e The advantage of the embodiment of theinventionshown in Fig's. 3 and 4,` is that the lid and the regulating deviceconstitute one unit, exchangeablewhen necessary. In order to preventthe'valve and the regulating device !rom .being damaged when the lid iscarelessly handled. the` lid is provided with an annular flangefll atthe body is'in its upper position, as shown in Fig; 4.

However, the openings 32 and 35 have' such rela tive positions and thevalve body is dimensioned in such away that the openings 32 are 'shut bythe valve body when 'it is'in its lowest position'.

The'valve body is 'kept in its upper position by a pin`36, made from ametal, fusible at a certain 4 temperature, which temperature theescaping flue' gases are not to exceed. If the fiue gases' reach,

thistemperature limit, the pin melts and', 'o'wing toits own weight, thevalve body'falls.;dow n to its lowest position shutting off the passageoi' flue numberof holes, it is,or course, possible to provide one singleopening in the flange Il, which can .be closed by the valve'body 134.

.The construction-of the regulating device illustrated in Figs. 3 and4'is naturally only'shown as an example and-may be varied in many dii'ferent ways within the limits of the invention. i For instance, as shownin- Fig; 5, the hot plate ll' may be made thicker than indicated inFig."4, and the height of the lid, 'including' the flange IS', may bemade equal to thethickness o'f the tion wall unnecessary and -thetupperedge of-the wall may thus be straight'and in contact with both the hotplate and the lid. The advantage` of this arrangementis that it'allowsthe'hot, plate to slide. Ireely due to heat expansion of the other partsof the stove. Inthis case.. howevcr, the flue gases must enter the lidfrom beneath, pass the valve, and escape downwards onthe other side'ofwall li'. This necessitates, oi course, the eliminationof the plate' 33,but the` flange li' is still in close' contact with the wall' li' asshown to 5 the desired temperature ot the flue gases is obtained bysetting the ,holder 22 in acertain positionby means of the lever 23 andthe adflue gases pass Ireely through-the opening in the' flange IS. II,on the other hand, the` temperature oi' the" flue gases should riseabove themaximum limit, the valve is closed, thus preve''ti'ng'justingscrew 26, However, especially when the temperature 'is to be`regul ated from a 'place at some distance, the use ot such a'method forvariation of the regulatingtemperature is rather impractical; Tue'`variation 'of the regulation temperature is attained in a simpler `andmore reliable way u the regulating device is con Instead of a In theregulating device accordingmgs; 3

uses" strip is constructed in such a waythat it closes the opening 'IIat a 'lower temperature. for instance slightly above 250 C. In thecylinder 12 there is another opening 'll placed opposite a channel 19arranged in a part' of the wall of the flue pipe that tits tightlyagainst the cylinder. The channel s opensinto the flue or the outletside of the cylinder 12, and may be closed by means of a valve 80, whichmay be adJusted from the front side of the stove by means of a'spindleIl threaded in the wall of the flue.

Any flue gases flowing through the flue i are forced to pass through theopening 14 and there-R' lating at the lower temperature, is uncovered inafter through either of the openings '15 or 18.2

or through both of them. When the channel 19 is completely' closed bythe valve 80, allof the flue gases-having passed the opening 14, passesthroughthe -opening 15.. The bimetal strip 11, however, closes thisopening when the flue gases have attained a temperature siightly above250 causing the draft to cease and the development of'heat in the flrebox of the range to be reduced. The temperature of the'flue gases canthus not rise higher than slightly above 250, nor can the temperaturefall considerably below this temperature, and the bimetal strip 11 tendsto maintain a constant temperatureof the flue gases of about 250; ,Theregulating temperature of the bimetal strip is thus about 250.

If it is desired to obtain an increased emission:

of heat in the stove, the temperature of the flue gases may, however, beraised' by 'opening the valve 80. The flue gases can then pass throughthe channel s and flow through the flue to"the chimney of the stove inspite of the fact that the opening is closed. Theirtemperature may nowrise to slightly above 300?, at which temperature the bimetal strip 'llcloses the opening 14. The bimetal strip 'IC thereafter tends tomaintain the flue gases at about 300, which is the regulatingtemperature, of this bimetal strip.

It is thus possible, bygadiusting the vaive 80 to closed or openposition to obtain regulation at a temperature of the flue gases ofeither 250 or 300". In view of the fact that for this adjustment nomechanical actuation whatsoever of the bimetal strips is required !romthe outside, 'the structure with the bimetal strips contained thereinmay be made as a separate unit that is easy to remove from the stove.For this purpose the cylinder is attached by means of a rod 82 to thelid M' that covers an opening in the hot plate i, this opening having aslightly larger diameter than the cylinder so that this may be lifted,together with the lid, through the opening and removed for cleaning orexamination.

In the embodiment of scribed, the openings 14 and 15, through which theflue gases flow, are arranged in series. It is, however, also possibleto arrange the openings "4' and 15' in parallel, as shown in Fig. 11. Todo this, the bimetal strip regulating at the higher temperature isarranged so that it may be rendered inoperative. This may be done byclosing the opening 14', regulated by this strip, by means of somesuitable arrangement. In the arrangement shown in Fig. 11, the cylinderflts tightly against the walls of the flue so that with the exception ofthe openings in the cylinder the flue is completely shut off. Part ofthe wall 84 of the flue has a cyllndrical surface corresponding to theouter surface of the cylinder 12' and has a greater peripheral extentthan the opening 14'. If the cylinder is in the position shown in Fig.11, the opening 'M' is situated opposite the invention above de-`bimetal strip 16 this position of the cylinder and is in a` position toreceive the flue gases which can enter' the cylinder through thisopening only. For the escape of the flue gases from'the cylinder an'additional opening 85 is arranged. The flue gases will thus passthrough the openings `'II' and u and hence are r'egulated by -thebimetal strip 11, so that their temperature remains constant at about250,which is the regulating temperature ofthis bimetal strip.

The cylinder 12' is arranged in sucha way' that it can be'turned in thedirection shown by the arrow Ato-'such a position that 'both theopenings'N' and 15' becomeuncovered and may serve as inlets. The dimensionsof'the openings are such that,*wh en turning the cylinder'to thisposition, the opening 85 remainsopen; Theflue gases'may thus pass intothe cylinder through the openings 'll' and 'II' and escape from .it

through the opening 85. When the flue gas temperature has risen toslightly above 250 the opening 15' is, however, completely closed by thebimetai strip 'Il',"and the flue gases may thereafter 'only pass throughthe opening 'il',

but in doing so they are regulated bythe bimetal strip-16' arranged atthatf'opening so that their temperature' remains constant at about` 300.Hencein this embodiment of the invention it is thus possibletoadiustflthe temperature of the flue gases, as required, to the higher orthe lower regulating temperature. cylinder 12' may also be rotated in aclockwisedirection 'from the position shown in Fig. 11, as indicated bythe arrow B, so that opening 15' is closed by the wall u. In thisposition, opening 85 constitutes the inlet to cylinder12' and opening14' the flow of-fl'ue bimetal strip 16', temperature. V p

It 'has been supposed in the above, in connection with Figs; &and 10,that the valve 80 has either been;completelyclosed, in which case theregulation has taken place at the lower regulating temperature (250), orelse completely open, in which case the regulation has taken place atthe higher regulating temperature (3007)' In the former case the bimetalstrip 11 alone, and in the latter case the bimetal strip 'IS alone, hasbeen supposed to efl'ect the regulation. This is, however, not actuallythe case in practice. When the valve 80 is closed it is principallythe'bimetal strip 11 that effects the regulation but also the has someinfluence as this also as is controlled. solelyby the 4 becomes deformedattemperatures below 300.

15. In order to bring At a temperature of the flue 'gases of 250 thefree end of the bimetal strip 18 is, however, situated at acomparatively long distance from the opening 14, and therefore thesedeformations have little influence on the regulation. If the valve isopened somewhat, part of the flue gases will pass through the channel 'sand a small amount of flue gases through the opening about that the sametotal amount of flue gases will pass through the flue at the samedifference in pressure, it is then necessary to reduce the eifectivearea of opening 15, which means that this must be further throttled bythe bimetal strip 'I In order to do this it is, however, necessary thatthe temperature of the flue gases should rise somewhat. This, on theconstitutes the outiet. Hence;

which regulates at the higher tute shall be raised or lowered.

other hand. entails that the ibimetal strip I 'II further approaches itsclosed position'and zreatly ailects the iregulation. I! the valve 80 isopened. this thus entails as a consequenoe that 'the ini fluence of thebimetal strip 11. on the regulation is reducedwhile the influence of thebimetal a strip 'IC increases, causing the `rexzulatirg temperature torise; The more the valve is opened',

' the bigger the influence of the bimetal strip 16 on the regulation,andthe bigger the rise 'of when the valve 80 is opened theregu atinatemperature thus rises continually from about 250 to about 30.-and anyintermediate regulat ing temperature may b obtainedh the valve is Whatweclaim'isr l. In a combustion device. aflue. means for heat insulating'said fluega bimetallic thermostatic element` disposed in said flueadjacent to an opening.:therethrough and constructed and v arranged' sothat change lnshape of said element' 4 'the regulatingtemperature. Witha wholly open valve the flue gas temperature is regulated .pracx tiallyexclusivelyby' thisbimetalstrip.:

due to' temperature changes varies its distance' from said opening toregu atethe flowor gas through' the open1ng,- and means for ,subjectingsaid element tovariable quantities of air at sub-` stanti'allyatmospheric'temperature.

` element positioned to'cover ami uncover :said

openedijto a suitable degree; ;It is further eviu dent that the bimetalstrip 16 or;`|'|- does not i actually' regulate at a. certain'.temperaturebut within'a certain rangeoftemperaturelying about i 300loi-;2503 respectively; In the same way a i der 125;

I contlnual 'alteration ot the regulating temperaw v j t'ure naturallybe obtained in the arrangei I ment according to l flt the cylin- 25,

It has been shown in above howi a mem-. ber' sensitive to' temperature(the bimetal strip 1.6 or 11 .respeotively), is` rendered inoperative rbyaopeninga by pass channel around the openlng`-`regulated by the;member,;orby closing thls I openinj; ;lt is, however, possibletosrender the w memberssensltive to temperature inoperative in 1other-ways, tor; instane by shielding. them from' the influence of the`flue gasesby means of screens.

The bimetal strips ay also be rendered Inactive 1 by being held' inclosed oi"` open position g .gAnynumber o! members 'sensitive totempera-;1 ture, egulating at diflerenttemperatures and actuating' the same orseparateregulating organs,

may beiused these members being put out o! action in`pro'pe'r order astheregulating tempera-' "While wehave shown severalembodiments ofourinventl on, it is .to beunderstood that` this 4 .has been done`for`nurposesgot illustration-only.

and that "the v sco'pe ot our: inventionis to 'be member, said'flueleadingitrom "said flre box to an outlet. saidove'n and'said platemember being positionedin'heat exchange-'relatmn with said flue amoveable *draft regulatingmember in said flue 'positioned betweensaid-'fire box' 'and' said outlet, means-!or heat insulatin'g, thatportion of said flue'that extends'between said flrefl box and saidregulating member, `in a mannei'` whereby a sufllcientlyligh temperaturemay be maintained' in sald portion to prevent an'deposit of soot orcondensation withinsaid flue in an amount that would obstruct the freemovement of said regulating member; and means re- V sponsive tovariations in temperature fo' erating said regulating' member. said.responsive means being in directmetallic* heat transfer relation withsaidoven' and said plate and its ad-" y joinlngmember, and in 'proximateheat transfer relation with the gases lnsaid flue.

i GUSTAF DALN.: y

;GEORG omsom restrictive

